1. Field of The Invention
This invention relates to a process for preparing .beta.-nitroethanethiol. The compound has been discovered to be useful in the novel synthesis of biotin as described in U.S. Pat. application Ser. No. 591,597 for Preparing Biotin (M. Marx and J. Reisdorff) filed June 30, 1975.
Prior Art
The compound .beta.-nitroethanethiol is known in the prior art (see for example R. L. Heath and A. Lambert, J. Chem. Soc., 1477[1947]). Past attempts to prepare .beta.-nitroethanethiol [IV] from a readily available starting material, e.g. .beta.-nitroethanol, [I] have resulted in yields of at best about 10%, and have necessitated isolation of the highly reactive intermediate nitroethylene [III] (cf., inter alia, the reference cited above). For example, reaction of .beta.-nitroethyl acetate [II] with potassium hydrogen sulfide leads exclusively to bis-nitroethyl sulfide [V] rather than to .beta.-nitroethanethiol, [IV] and even the reaction of purified nitroethylene (prepared in .about.50% yield from .beta.-nitroethanol) with hydrogen sulfide is reported to produce only 18% of .beta.-nitroethanethiol accompanied by 48% of the aforementioned bis-nitroethyl sulfide. These reactions and the intermediates are set forth in the reaction scheme following. ##EQU1##
We have discovered a novel method for preparing nitroethanethiol in significant yields using an elegantly simple process.